1. Field of the Invention
This invention relates to a method of hydrolyzing chlorosilicon compounds. More specifically this invention relates to a method of hydrolyzing polyfunctional chlorosilicon compounds to obtain gels that are nonsticky and easily handleable.
2. Description of the Prior Art
A wide variety of commercial silicone polymers are produced by the hydrolysis of a few basic organochlorosilanes. These important organochlorosilane monomers are produced by processes that also yield minor amounts of by-products. For example, methylchlorosilanes are obtained from the reaction of methyl chloride with silicon by what is commonly called the "direct process" method. The by-product from this process is a mixture containing many polyfunctional chlorosilicon componds and is essentially useless. The eventual disposition of these by-product chlorosilicon mixtures has become a significant problem as the production volume of silicone polymers has increased. Considerable expense and difficulty is presently encountered when this by-product is incinerated because of its high chloride content.
It is taught in Great Britain Pat. No. 1,173,022 that chloride contained in the direct process by-products can be removed by either of two methods: (1) introducing sodium bicarbonate into the by-product and removing the sodium chloride produced, or (2) alkoxylating the by-product with an appropriate alcohol to split off hydrogen chloride.
It is known from U.S. Pat. No. 3,090,765 that the hydrolysis of chlorosilanes having one or less organic radicals per silicon atom results in separation of gel from the water. This gel deposits on the walls of the hydrolysis vessel and on the stirring apparatus. It is difficult to remove from the reaction vessel and presents a serious handling problem.
Techniques which prevent gelling have been developed to control the hydrolysis of chorosilane mixtures averaging one or more organic radicals per silicon atom for the production of commercial polysiloxane resins. It is taught in U.S. Pat. No. 2,398,672 that improved polysiloxane resins may be obtained by dissolving the chlorosilanes in a hydrocarbon solvent and adding the solution to a two phase mixture of water and a partially soluble alcohol. Alternatively, U.S. Pat. No. 2,470,497 teaches the addition of chlorosilanes to a hydrolysis medium of water, hydrocarbon solvent and a glycol either type solvent. These processes are not economically attractive for the hydrolysis of polyfunctional chlorosilicon by-products because they require relatively large amounts of organic solvents.
It is an object of this invention to provide a method of hydrolyzing polyfunctional chlorosilicon compounds that produces a gel that is non-sticky and easily handleable. Another object of this invention is to provide a method whereby polyfunctional chlorosilicon compounds can be economically hydrolyzed to greatly reduce the chloride content prior to disposal. Still another object of this invention is to provide a method of hydrolyzing polyfunctional chlorosilicon compounds whereby hydrogen chloride may be recovered.